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🎯 Main Points

Chapter 32

PSYP610 - Neurological Bases of Behavior

🔑 Key Definitions

Dopamine (DA): Monoamine neurotransmitter involved in movement, motivation, reward, and cognition
L-DOPA: Dopamine precursor used to treat Parkinson's disease; crosses blood-brain barrier
Nigrostriatal Pathway: Dopamine pathway from substantia nigra to striatum; degeneration causes Parkinson's
Mesolimbic Pathway: Dopamine pathway from VTA to nucleus accumbens and limbic areas; involved in reward and schizophrenia

🧠 Dopamine Synthesis Pathway

  • Phenylalanine: Essential amino acid from diet
  • → Tyrosine: Converted from phenylalanine
  • → L-DOPA: Tyrosine hydroxylase (rate-limiting enzyme)
  • → Dopamine: DOPA decarboxylase removes carboxyl group

📊 Three Major Dopamine Pathways

  • Nigrostriatal: Substantia nigra → Striatum; motor control; loss causes Parkinson's disease
  • Mesolimbic: VTA → Nucleus accumbens/limbic; reward, motivation; overactivity linked to schizophrenia
  • Tuberoinfundibular: Hypothalamus → Pituitary; inhibits prolactin release

📊 Receptors & Disorders

  • D1 Receptors: Excitatory; increase cAMP
  • D2 Receptors: Inhibitory; decrease cAMP; target of antipsychotic drugs
  • Parkinson's Disease: DA deficiency in nigrostriatal pathway; treat with L-DOPA
  • Schizophrenia: Excess DA activity in mesolimbic pathway; treat by blocking D2 receptors

📊 Dopamine Deactivation

  • MAO (Monoamine Oxidase): Enzyme that breaks down dopamine inside neuron
  • COMT (Catechol-O-Methyltransferase): Enzyme that breaks down dopamine in synaptic cleft
  • Reuptake: DAT (dopamine transporter) pumps DA back into presynaptic terminal

💡 Exam Tips

  • Remember synthesis: Phenylalanine → Tyrosine → DOPA → Dopamine
  • Three pathways: Nigrostriatal (movement), Mesolimbic (reward), Tuberoinfundibular (hormones)
  • Parkinson's = TOO LITTLE DA (nigrostriatal), Schizophrenia = TOO MUCH DA (mesolimbic)
  • L-DOPA crosses blood-brain barrier, dopamine doesn't - that's why L-DOPA used as treatment
  • D2 receptor blockers = antipsychotics (but can cause Parkinson-like side effects)
  • MAO and COMT both break down DA - MAO inhibitors used as antidepressants